The boy, Chase, was adopted three months ago from Russia, police said.

Miles Harrison, 49, of Purcellville was charged yesterday with manslaughter. He faces up to 10 years in prison if convicted.

Dave Zorger, owner of Herndon-based Project Solutions Group, where Harrison is managing director, said someone went to the front desk at the end of the day Tuesday and told the receptionists about seeing something in a GMC Yukon with tinted windows parked outside.

"They said, 'Hey, Miles, is there something in your car?' and he went running outside," Zorger said.

Herndon Police Chief Toussaint E. Summers Jr. said Harrison was supposed to take Chase to day care. Instead, Harrison drove to work, and Chase sat in the SUV outside the building, in the 500 block of Herndon Parkway, for "at least several hours," Summers said. Exactly how long remains unclear. The high temperature Tuesday was about 90 degrees.

Zorger said Harrison arrived at work at the real estate consulting firm "sometime in the morning," and police said they received an emergency call about 5 p.m. that someone was performing CPR on an unresponsive child.

Summers said authorities think the manslaughter charge is appropriate. The investigation is continuing, he said.

"You can't leave a kid unattended," he said.

Summers would not say what investigators think happened. "Manslaughter is simply the unlawful killing without malice," Summers said. "It's really hard to know what was going on in Miles Harrison's mind at that point."

Zorger said he did not know whether some distraction might have contributed to the boy's death.

"I wish I knew the answer to those questions. Those are the same things I'm asking myself," Zorger said.

John Alexander Gomez, who works for a financial firm in the same green-and-gray building in the Herndon office park, said he was leaving for the day when he saw paramedics put the child's limp body in a white bag.

"That's a terrible death . . . with the heat. When I got in my car at 1, my steering wheel, you couldn't touch it," Gomez said. "To me, that's proof right there. You can't do too many things at once."

Evelyn Rivas, who works in the same building and has a 6-year-old daughter, said it was unthinkable that she would be in Harrison's situation. "I have a kid, and I don't think I'd forget they were in the car," Rivas said. "It seems to me a lot of people do it. It doesn't make sense."

Harrison was taken to a medical facility after rushing out to the child, and he was to be taken into custody there yesterday, Summers said.